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Effects of Cold Weather on Mortality: Results From 16 European Cities Within the PHEWE Project

Analitis, Antonis*; Katsouyanni, Klea*; Baccini, Michela; Kassomenos, Pavlos; Kirchmayer, Ursula§; Cadum, Ennio; Hojs, Ana; Kriz, Bohumir**; Pekannen, Juha††; Woityniak, Bogdan‡‡

ISEE/ISEA 2006 Conference Abstracts Supplement: Symposium Abstracts: Abstracts

*Department of Hygiene and Epidemiology, University of Athens Medical School, Athens, Greece; †Department of Statistics, University of Florence, Florence, Italy; ‡Department of Astrogeophysics, University of Joannina, Joannina, Greece; §Department of Epidemiology Local Health Authority ASL RM/E, Rome, Italy; ¶Regional Environmental Protection Agency, Grugliasco, Italy; ∥Department of Environmental Health, National Institute of Public Health, Ljubljana, Slovenia; **Department of Epidemiology, Charles University, Prague, Czech Republic; ††Unit of Environmental Epidemiology, National Public Health Institute, Kuopio, Finland; and the ‡‡Department of Medical Statistics, National Institute of Hygiene, Warsaw, Poland


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In the framework of PHEWE study, we investigated the short-term effects of meteorologic conditions on daily mortality and morbidity. Data from 16 European cities are used providing daily measurements for meteorologic variables. Confounding effects of air pollution and chronologic variables were considered. The analysis was carried out separately for warm (April–September) and cold (October–March) period and was focused on the effect of apparent temperature on health. We report the results related to effects during the cold period.

A hierarchical modeling approach was used. First, regression models were fitted in each city separately to allow specific control for weather and other potential confounders. Results of the individual city analysis were used in a second stage analysis to provide overall estimates.

The city-specific analyses were based on the generalized estimating equations (GEE) approach, assuming Poisson distribution on the outcome. For each participating city, we fitted a model with outcome variable the daily number of deaths and several covariates: apparent temperature, confounders (dummy variables for holidays, day of the week and calendar month, air pollution), and other meteorologic variables (barometric pressure, wind speed). We assumed that observations during 1 year were correlated, whereas observations of different years were independent.

The exposure–response curve between apparent temperature and daily mortality shows a linear relationship with negative slope in cold period. One-percent increase in the daily total number of deaths is associated with a 1° decrease of apparent temperature (P < 0.001). The corresponding increase for the cardiovascular and respiratory number of deaths is 1.4%.

Effect modification due to geographic areas and climatic zones as well as other variables was assessed. Interactive and confounding effects of air pollutants (particulate matter, ozone, and NO2) were also investigated.

The PHEWE results are based on the largest database used for Europe until today and provide quantitative effect parameters, which can be used for prevention and public health policy.

© 2006 Lippincott Williams & Wilkins, Inc.